November, 1923
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
Determination of Ash, Arsenic, Copper, and Zinc in Gelatin Editor of Industrial and Enginezring Chemistry: We have read with much interest, the article of Roger M. Mehurin, entitled “Determination of Ash, Arsenic, Copper, and JOURNAI,, 15,942 (1923)l. As a result of Zinc in Gelatin” [THIS the analyses in our laboratories of some ten thousand samples of gelatin during the past fifteen years, we do not feel t h a t the conclusions of the author of t h e above-mentioned article are warranted. I n the first instance, t h e amount of sample t o be taken for 10 gramsanalysis as recommended by Mr. Mehurin-namely, is entirely inadequate for the accurate determination of the minutc! amounts of copper and zinc present in most samples on gelatin; and in many cases this also applies t o the determination of arsenic. It follows, then, t h a t on a suitably large sample, 50 t o 100 grams, the ashing procedure is impractical. We have found from our experience t h a t the methods as outlined by the Association OF Official Agricultural Chemists, in J . Assoc. O f i cial Agr. Chem., 5 , 343 (1922), and revised t o date by Claude R. Smith, of the Bureau of Chemistry, offer a simple, reliable, and accurate method of procedure for t h e determination of the above-mentioned impurities. We have found that, if ordinarycare in manipulation and proper technic are used, there is never any difficulty experienced in the saturation of the solution with hydrogen sulfide nor in its subsequeiit filtration. Referring t o the statement in the article by Mr. Mehurin, t h a t “the determination of copper by titration with sodium thiosulfate is open t o a considerable error because of the difficulty in obtaining a definite end point when small amounts of copper are titrated,” we do not agree with the author in this respect. This objection has often been raised in our experience, and we have always been able t o demonstrate t h a t with proper technic i t is possible t o obtain end points which are sharp and remain so for half a n hour or more. Furthermore, numerous blank and check determinations have shown conclusively t h a t the method can brb relied upon t o give accurate results. We have no criticism t o make of the method for the determination of arsenic given by Mr. Mehurin, as we do not feel t h a t there is any very essential difference between i t and the A. 0. A. C. method. IRVING HOCHSTADTER HOCHSTADTER LABORATORIES
NEW Y O R K
CITY
September 12, 1923
1197
requiring any attention whatever during the ashing process. From this point i t has been the experience of t h e writer t h a t a n appreciable time is saved in handling small volumes of solution containing small amounts of inorganic salts rather than large volumes containing large amounts of organic material. I n regard t o the copper determination, the writer has often experienced difficulty, as have others, in obtaining a definite end point when titrating very small amounts of copper with thiosulfate, and has obtained much more uniform results with the colorimetric method. I n conclusion, it may be stated t h a t the method was not offered with any intention of supplanting or criticizing the accuracy of the tentative A. 0. A. C. method (with the possible exception of the above-mentioned copper titration), b u t merely with the thought t h a t i t would be found t o be less time-consuming in cases where it is necessary t o analyze a large number of samples simultaneously. I n this connection i t may be mentioned t h a t this method has been employed for some time past, in preference t o all others, by the laboratory of one of the largest gelatin and glue works in the country. R. M. MEHURIN BURGAUO F ANIMALINDUSTR; ~ A S I I I N G T O N , D. c. September 17, 1923
New Treatment for Gasoline I n his address before the Mid-West Section of the Society of Automotive Engineers i n Chicago, October 12, C. F. Kettering, president of the General Motors Chemical Company, announced t h a t this company and the Standard Oil Company (Indiana) had entered into a contract for the distribution of ethyl fluid. Ethyl fluid is the new addition agent for gasoline, and has the effect of increasing engine efficiency and taking the knock out of a n engine, no matter under what conditions or load a n automobile is driven. It is t h e result of several years’ research and test at the laboratories of the General Motors Research Corporation in Dayton, and has met with enthusiastic reception from motorists in Dayton and in Cincinnati, Ohio, where it has been placed on sale a t a few stations. Gasoline treated with ethyl fluid has a characteristic light wine color, which distinguishes it from other automobile fuels. Distribution by the Standard Oil Company (Indiana) will cover the States of Indiana, Michigan, Illinois, Minnesota, Wisconsin, Iowa, Missouri, Kansas, South Dakota, and North Dakota as soon as installation can be made. The southern p a r t of the distributing territory is being equipped this winter and the northern part will be equipped a s early a s possible in the spring, in order t h a t motorists may be supplied when the 1924 motoring season opens. It is believed t h a t all the Indiana company service stations will be open and ready t o supply the treated fuel by July 1, 1924.
Dictionary of Specifications Editor of IBdustrial and Engineering Chemistry: Referring t o Mr. Hochstadter’s letter of September 12, published above, i t will be noted t h a t a 20 t o 40-gram sample of gelatin, and not 10 grams, is specified for the determination of copper and zinc. I n the tentative A. 0. A. C. method referred t o by Mr. Hochstadter, and of which he approves, practically the same in the range of sample is used-namely, 20 t o 50 grams-and Hertwig method [ J . Assoc. Oficial Agr. Chem., 7, 41 (1923)l a 20-gram sample is specified. No such range of sample a s 50 to 100 grams is mentioned in any method for the analysis of gelatin and glue t h a t has come t o the attention of the writer. Since the metals are usuallyinsolution with the gelatin during manufacture, they are uniformly distributed in t h e finished product and therefore as little as 20 grams of the mixed sample will usually be found sufficient. A perfect ash will be obtained if the directions are followed, and as many as twenty samples can be added directly t o a furnace 4 x 6l/, x 16 inches without previous charring and without
The work which the Bureau of Standards is carrying out on a dictionary of specifications has made good progress. During t h e past month existing specifications have been collected from more than 75 per cent of the important national technical societies, trade associations, and governmental publishing agencies t h a t have issued specifications. Leaving out all duplications, it would appear t h a t about 5000 specifications are available from these sources. However, not all of these specifications can properly be classed as related t o commodities purchased by t h e Federal, State, and Municipal Governments and public institutions. It is believed t h a t about 20,000 commodities do come within this class and of these more than 75 per cent of all commodities purchased for Government consumption are not covered b y available specifications. Work is being expedited on the collection of existing specifications with t h e object of making t h e collection as complete as possible so t h a t the first step in t h e preparation of t h e dictionary, the issuance of a classified list of existing specifications, may soon be taken. This will be of considerable service t o all agencies interested in this subject, and with t h e cooperation of the advisory board will be used as the basis for selection of specifications. for inclusion in the dictionary.
